The present invention relates generally to a wheel hub system which retains wheels on commercial vehicles, and more particularly to a system employing a threaded connector which mates with a wheel hub opening having a bolt stop.
Conventionally, wheel hubs are made out of ductile iron or aluminum, which are machined and assembled to mate with other components of a vehicle. For example, FIGS. 2 and 2A provide a view of a generally bell-shaped prior art wheel hub H attached in a conventional manner to a vehicle axle (not shown). A connector, such as a stud or bolt B extends through a bored cylindrical hole C defined by a mounting flange D of hub H. Typically a plurality of holes C are equally spaced around the periphery of the wheel hub mounting flange D, each receiving a bolt B.
The bolts B are used to secure together the hub H, sometimes a brake drum (not shown), and a wheel (not shown) upon which is mounted a tire (not shown). The bolts B each have a head J at one end, and a threaded portion K at the opposite end. A wheel nut (not shown) engages the bolt threaded portion K to secure the wheel to the hub H. The bolt B has a serrated shoulder portion M which is typically press-fit into cylindrical hole C to affix the bolt to hub H. The bolt head J has undersurface N, which is substantially perpendicular to a longitudinal axis of bolt B, and is seated substantially flat against the hub inboard surface E.
A vehicle wheel hub H is typically subjected to two types of stress which limit service life: (1) the mean stress imparted by tightening the wheel nuts, which has the effect of drawing the hub inboard surface E down into hole C; (2) stress caused by the serrated surface of the threaded bolt resisting rotation in the opening in the wheel flange due to the interference fit of the serrated portion of the bolt in the wheel flange opening. The combined stresses have a negative impact on the service life of the wheel hub H. Additionally, it is quite common for mechanics to over-tighten the wheel nuts when changing tires, resulting in over-stretching or over-tensioning the bolts B and further increasing the stress, which shortens the service life of the wheel hub H.